Radiofrequency/microwave (RF/MW) irradiation exerts strong biological effects in both animals and humans. RF/MW causes birth defects and behavioral deficits in neonatal rats. Although RF/MW exhibits both thermal and non-thermal effects, it has been hypothesized that the concomitant maternal hyperthermia causes the reproductive effects. RF/MW hyperthermia differs from conventional heating by penetrating biological tissues rapidly and heating from inside to the outside by diathermy. To date, no well controlled investigations have been published which contrast the teratologic or cytologic effects of equivalent hyperthermia induced by conventional and RF/MW methods. Furthermore, neither the role of nonthermal effects nor the major site of action which causes reproductive failure (whether in the embryo, or in the placenta, or caused by altered maternal metabolism) has been established. We propose to analyze effects of 27.12 MHz RF irradiation on gestational day 9 pregnant rats and their placentae. These findings will be contrasted with the effects seen (1) in pregnant rats which received an equivalent dose of conventional hyperthermia (immersion of a 42 degree C water bath) and (2) in pregnant rats which were irradiated, but prevented from becoming hyperthermic. The parameters to be analyzed include: (1) Gross teratology on gestational day 20; (2) Light and electron microscopy of embryonic neuroepithelium and placental tissues at intervals after treatment to identify early morphologic signs of pathology; (3) Determination of the proliferative characteristics of neuroepithelium after treatment; (4) Direct effects on embryos versus maternal metabolism will be sorted out by whole embryo culture of rat embryos in rat serum taken either from control, RF/MW or water bath treated rats; (5) Potential perturbations of DNA metabolism in all groups by means of 3H-thymidine incorporation of high pressure liquid chromatography. Due to the widespread use of 27.12 MHz RF irradiation in industry (presenting a potential hazard during pregnancies) the mechanism of the reproductive effects in experimental animals must be elucidated so that safe exposure levels can be established and teratogenesis can be either avoided or scientifically managed subsequent to exposure.